First step in reducing the size of PC descriptors.

runtime/vm/flow_graph_compiler_arm64.cc

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_ARM64.
 #if defined(TARGET_ARCH_ARM64)
 
 #include "vm/flow_graph_compiler.h"
 
 #include "vm/ast_printer.h"
@@ skipping 952 matching lines @@
     const Register function_reg = R6;
     new_pp = R13;
 
     // Set up pool pointer in new_pp.
     __ LoadPoolPointer(new_pp);
 
     // Load function object using the callee's pool pointer.
     __ LoadObject(function_reg, function, new_pp);
 
     // Patch point is after the eventually inlined function object.
-    AddCurrentDescriptor(PcDescriptors::kEntryPatch,
-                         Isolate::kNoDeoptId,
-                         0);  // No token position.
+    entry_patch_pc_offset_ = assembler()->CodeSize();
+
     intptr_t threshold = FLAG_optimization_counter_threshold;
     __ LoadFieldFromOffset(
         R7, function_reg, Function::usage_counter_offset(), new_pp);
     if (is_optimizing()) {
       // Reoptimization of an optimized function is triggered by counting in
       // IC stubs, but not at the entry of the function.
       threshold = FLAG_reoptimization_counter_threshold;
     } else {
       __ add(R7, R7, Operand(1));
       __ StoreFieldToOffset(
           R7, function_reg, Function::usage_counter_offset(), new_pp);
     }
     __ CompareImmediate(R7, threshold, new_pp);
     ASSERT(function_reg == R6);
     Label dont_optimize;
     __ b(&dont_optimize, LT);
     __ Branch(&StubCode::OptimizeFunctionLabel(), new_pp);
     __ Bind(&dont_optimize);
   } else if (!flow_graph().IsCompiledForOsr()) {
     // We have to load the PP here too because a load of an external label
     // may be patched at the AddCurrentDescriptor below.
     new_pp = R13;
 
     // Set up pool pointer in new_pp.
     __ LoadPoolPointer(new_pp);
 
-    AddCurrentDescriptor(PcDescriptors::kEntryPatch,
-                         Isolate::kNoDeoptId,
-                         0);  // No token position.
+    entry_patch_pc_offset_ = assembler()->CodeSize();
   }
   __ Comment("Enter frame");
   if (flow_graph().IsCompiledForOsr()) {
     intptr_t extra_slots = StackSize()
         - flow_graph().num_stack_locals()
         - flow_graph().num_copied_params();
     ASSERT(extra_slots >= 0);
     __ EnterOsrFrame(extra_slots * kWordSize, new_pp);
   } else {
     ASSERT(StackSize() >= 0);
@@ skipping 80 matching lines @@
     for (intptr_t i = 0; i < num_locals; ++i) {
       // Subtract index i (locals lie at lower addresses than FP).
       __ StoreToOffset(R0, FP, (slot_base - i) * kWordSize, PP);
     }
   }
 
   VisitBlocks();
 
   __ hlt(0);
   GenerateDeferredCode();
+
   // Emit function patching code. This will be swapped with the first 3
   // instructions at entry point.
-  AddCurrentDescriptor(PcDescriptors::kPatchCode,
-                       Isolate::kNoDeoptId,
-                       0);  // No token position.
+  patch_code_pc_offset_ = assembler()->CodeSize();
   __ BranchPatchable(&StubCode::FixCallersTargetLabel());
 
-  AddCurrentDescriptor(PcDescriptors::kLazyDeoptJump,
-                       Isolate::kNoDeoptId,
-                       0);  // No token position.
+  if (is_optimizing()) {
+    lazy_deopt_pc_offset_ = assembler()->CodeSize();
   __ BranchPatchable(&StubCode::DeoptimizeLazyLabel());
+  }
 }
 
 
 void FlowGraphCompiler::GenerateCall(intptr_t token_pos,
                                      const ExternalLabel* label,
                                      PcDescriptors::Kind kind,
                                      LocationSummary* locs) {
   __ BranchLinkPatchable(label);
   AddCurrentDescriptor(kind, Isolate::kNoDeoptId, token_pos);
   RecordSafepoint(locs);
@@ skipping 612 matching lines @@
 void ParallelMoveResolver::RestoreFpuScratch(FpuRegister reg) {
   UNIMPLEMENTED();
 }
 
 
 #undef __
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM64